1. Field of the Invention
This invention relates to automation equipment directly connected to a TCP/IP communication network.
2. Description of the Invention
The IP (Internet Protocol) standard protocol defines a protocol for interconnection of communication networks at the network layer. The TCP (Transport Control Protocol) standard protocol defines a data transport mechanism that guarantees end to end routing. These two protocols that are widely used in Internet, Intranet or Extranet type global networks are grouped under the term “TCP/IP network” in this presentation.
In the following, automation equipment denotes a programmable logic controller, a monitoring/control station, a digital control or any equipment that may contain and execute an application program in order to check and/or control all or some of an automation application, for example belonging to the field of industrial logic controllers, building or monitoring/control logic controllers for electrical distribution networks. Automation equipment may also comprise industry specific modules that are also provided with a processing unit to perform particular functions related to an automation business (such as weighing, regulation, positioning, etc.) and other modules such as input/output modules. Modules of automation equipment are connected together and synchronised with each other through an internal communication bus, usually called a back panel bus, that usually uses a proprietary protocol optimised for real time input/output exchanges.
In automation equipment, it is well known that a communication module can be arranged firstly connected to the internal communication bus of the automation equipment, and secondly to the TCP/IP network. This communication module creates a bridge between firstly the internal communication services and proprietary services, and secondly the TCP/IP network.
However, under these conditions, it is very complex to maintain the characteristics of a communication according to the TCP/IP protocol from end to end between two entities communicating with each other. The gateway for a network module cuts off the TCP data flow and does not make the IP transparent. The result is that the benefits in terms of performance, reliability and transparency provided by the TCP/IP protocol are lost.
Furthermore, a communication system in an automation equipment is known in which information exchanges conform with the TCP/IP protocol are possible on the internal communication back panel bus. The modules of the automation equipment have their own IP address and a TCP/IP stack that can be executed by the processing unit of these modules, in order to exchange information conform with the TCP/IP communication protocol. Furthermore, the automation equipment comprises a network module connected to an external TCP/IP network and to the internal back panel bus, that the automation equipment modules can use to make information exchanges conform with the TCP/IP communication protocol directly on the TCP/IP network, through the internal back panel bus.
Nevertheless, this solution uses the internal back panel bus of the automation equipment to route the TCP/IP communication, which can be harmful for the performances of real time communications related to the automation application, and also requires the use of a dedicated network coupler.